Can you help me find the slope of these queastions?

How many different ways can you make change for $.50 using only nickels,dimes, and quarters?

Josephine has a great garden with and area of 2x2 + x - 6 square feet

The general form of the quetion of a circle is ax^2+by^2+cx+dy+e=0 where a=b=0 if the circle has a radius of three units and the center lies on the y axis which set of values of a, b, c, d, and e might correspond to the circle